Scientists Mystified by Herring Decline
TACOMA, Wash. A steep decline in Puget Sound-area herring, a critical food source for larger fish, marine mammals and sea birds, has scientists mystified.
Not only are adult herring dying earlier than normal, but some fear a stock that used to be one of the largest in Washington state's inland marine waters could go extinct.
The 30-year decline in the small, silvery fish has far-reaching implications, said Jim West, a state Fish and Wildlife Department research scientist who found high concentrations of polychlorinated biphenyls and other toxic substances in herring in south Puget Sound.
"Virtually any predator worth its salt in Puget Sound is going to be eating herring," West said.
Herring are a dietary stable for chinook salmon, cod and halibut, and also are eaten by porpoises, seals, sea lions and orcas. Freshly spawned herring eggs once drew swarms of marine birds, especially diving ducks called surf scoters that fly north to nest in the Canadian interior.
"It's thought to be important for them to feed on herring spawn while they're here because there's not a lot of food up there for them," said Joseph Evenson, a state Fish and Wildlife Department biologist. "They're basically working off their fat reserves."
The herring decline may explain the disappearance of thousands of scoters from parts of the inland waters, said Evenson and his boss Dave Nysewander, the state's marine bird and mammal project leader.
One of the most severe herring declines is between Bellingham and the Canadian border, an area which once accounted for about a third of the state's total stocks.
The Cherry Point stocks plummeted from 10,000 tons in 1994 to 808 tons in 2000, then rebounded to 1,611 tons in 2003, but remain in danger of going extinct, said Duane Fagergren, a fish biologist with the state's Puget Sound Action Team.
In January 2004 the Center for Biological Diversity and other activists sought protection for Cherry Point herring under the Endangered Species Act. A decision from the National Oceanic and Atmospheric Administration is expected in mid-May.
Much of the mystery to scientists is in the high percentage of herring that die before reaching the age of peak fertility.
Herring in the inland waters typically used to live as long as 5 to 8 years, but now "it's rare to see one over 4," said Paul Hershberger, a U.S. Geological Survey fish pathologist who has been studying disease in herring since the mid-1990s.
In the 1970s, about 20 percent of the sound's herring population died of natural causes annually, but now it's 67 percent to 84 percent, Hershberger said.
Source: Associated Press